Magnetic pole



July 15, 1952 M. P. WINTHER 2,603,677

MAGNETIC POLE Filed Oct. 30, 1950 s Sheets-Sheet 1 July 15, 1952 M. P.WINTHER 2,503,677

MAGNETIC POLE Filed Oct. 30, 1950 3 Sheets-Sheet 2 FIGS.

M. P. WINTHER July 15, 1952 MAGNETIC POLE 5 Sheets-Sheet 5 Filed Oct.30, 1950 FIG. I4.

M F r W Patented July 15, 1952 1 2,603,677 'MA N QIR LE.

\ Martin. P. Winther,

ates Mills, Ohio, assignon This invention relates generallyto magneticpoles for dyn amoelectric machines, and more particularly, but withoutrestriction, to such poles for pole rings of toroidal magnet fieldsofdynamoelectric machines operating by means of eddy currents ininductor drums.

The invention is an improvement, upon constructions such as shown in theU. S. patent of Anthony Winther and myself, No. 2,470,596, dated May 17.1949.

Among the several objects of the invention is the preservation of theefllcient magnetic circuit disclosed in said patent but at the'same timeto reduce flux density at the magnetic gap of the machine, therebyreducing the magnetomotive force required to force the magnetic fieldacross the gap and also reducing the eccentric'pull-over between themagnetic field and rotor members of apparatusof the class described.Other objects will be in part apparent and in part pointedouthereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts which willbe exemplified in the structures hereinafter described, and the scope ofthe application of which will be indicated in the following claims.

In the accompanying drawings, in which, several of various possibleembodimentsof the invention are illustrated,

Fig. 1 is a half longitudinal section of eddycurrent apparatus embodyingthe invention;

Fig. 2 is a development ofseveral pole faces-on an enlarged scale, beingtaken on line 2-2 of Fig. 1;

Fig. 3 is a fragmentary detailv taken on line 33fof Fig. L'showing abottom plan view of one of the poles illustrated in Fig. 2;

Figs. 4, 5, 6 and 7 are cross sections. taken on lines 4-4, 5-5, 6-6 and1 ofFig. 2!;

Fig. 8 is a cross section ofv an alternative form of pole;

Fig.9 is an end elevation of the, pole shown in Fig. 8, viewed from itstoe-end;

Fig. 10' is a rear elevation of the pole shown in Fig. 8, viewed fromits heel end;

Fig. 11 is a plan view of the face of the, pole of Fig.8; and, h

Figs. 12, 13 and 14 are enlarged cross sections taken on lines 12-12,l3-l3 and I,4l4 of Fig. 11.

Similar reference characters indicatefcorresponding parts throughout theseve'ral. views of the drawings;

Referring now more particularlyto Fig. 1. there 3 Claims. (Cl. 172--284)is shown a longitudinal section of one formof dynamoelectric apparatusto which the invention applies. At numeral l' is shown the supportingframe, in which are two coaxial sleeves 3 and 5 in which are bearingsland- 9, respectively. The bearings 1 support a' rotary drive shaft iland bearings 9 support a rotary driven shaft l3. It will be understoodthat as is the case in all apparatus of this class, the driving anddriven relationship of shafts H and i3 may be reversed, thisconstitutinga mere inversion. 'Itwill alsobe understood that the drivenshaft may be stationary as in the case ofa dynamometer or brake.

Keyed to shaft l I is aspider 15 for supporting an annular field membershown generall at H. Keyed to the shaft I3 is a spider I 9 forsupporting a magnetizable eddy-current inductor drum 2| composed offerrous material. I

The annular field member Ilcomposed of two magnetizable fieldrings23-and 25, composed of ferrous material. These are welded to amagnetizable rim 21 ofthespider, alsocomposed of ferrous material."Between the rings 23 and 25 is an annular field coil 29-which isvariably excited by means'of-a suitable circuit led in through a conduitmeans 3-! from collector rings associated with the shaft H. Thecollector rings are not shown and require nofurther description,beingcommon in apparatus of thisclass.

The rings 23' and 25 are provided with notches, those for ring 23 beingshown at numerals'33, and those for ring 25 being shown at 35. Thenotches become wider and deeper along their lengths in the direction ofcoil 29. Each ring 23 and 25 between its notches has axially extendingpolar teeth of the so-calledclaw type, those for-ring 23 being indicatedat numerals 31 and those for ring 25 being indicated at numerals 39.These teeth extend in opposite directions to envelope thefield coil 29;and interdigitate as indicated in Fig. 2. The bottoms of the notches 33and 35 slope at an angle, for example, 35 to the axis of the machine.Likewise, an equal slope is given tothe bottom edges 41 of teeth 31 andbottom edges 43 of teeth39. Thusconstant spacingis left between theseedges 4| and 43 and the bottoms of the notches 35 and 33, respectively.

When the coil 29 is. excited, a toroidal flux field is established, asindicatedby the dash lines F. If the teeth 39 are 'qonsideredto be ofnorth polarity, then thistoroidal field may be traced as follows (seediagrammatic mean line F) from ring 25'through teethf39, into thedrum2|, back tO IJGQth 31, ring 23, rim 21 andbacl; to ring 25,. As shown atG, there is an air gap between the teeth 37 and 39 extending from therings 23 and 25. shaped and made according to the principles set forthin said Patent 2,470,596. That is, each tooth is so formed that the fluxdensity through any tooth cross section, which cross section issubstantially normal to the S-shaped parts of the mea flux path F, shallcarry substantially a constant flux density. The indicated S-shaped fluxpaths are shown at S. It will be understood that with any two adjacentpoles such as constituted by teeth31 and 39 there is interpolar fluxleakage and the stated cross sections are such that after said leakagehas been taken into account, thefiux density i each stated cross sectionis the same as the flux density for any other cross section. This makesmost efiicient use of the metal constituting the toothed poles andreduces weight. This feature of itself is not new herein, but isreferred to in order to show the point of departure of the presentinvention.

As in said Patent 2,470,596, one way of obtaining sections as specifiedin the paragraph above is to form the teeth as shown in Figs. 2, 3 and4. These teeth have substantially righttriangular bottom portions 45lying adjacent the coil 29. From the apexes of these triangles are thesloping edges H or 43, as the case may be. This results in the extendingtoe-ends T of the teeth flaring toward the inductor 2|. At the heelportions H, by reason of the shape of the notches 33 and 35, the teethflare away from the inductor 2| in the regions of the ring 23 or 25, asthe case may be. Further details may be obtained from said Patent2,470,596, it being unnecessary to repeat them here.

The point of departure of the present invention is that instead of theface areas A of the teeth also carrying the same flux density as theflux density throughout tooth sections normal to the s-shaped mean fluxpath, the face area of each tooth right at the gap G is enlarged, sothat the flux density in this face area exclusively is reduced belowwhat it is in every other of said sections. One manner of enlarging thisface area of a tooth is illustrated in the form of the invention shownin Figs. 1-7, wherein flanges 41 are superimposed along the leading andtrailing edges of the teeth. Each flange, as shown in Figs. 4-7, followsthe tooth contour from the region in which it flares away from theinductor 2| to where the tooth flares toward the inductor 2|. Forexample, in Figs. 3 and 7 the bottom of tooth 31 is show extending fromthe pole ring 23. The toe T of this tooth flares toward the inductor(Fig. 7) and the heel H flares away from it (Fig. 4). The flanges 41extend along theedges' in the heel and toe and substantially exclusivelyenlarge thelpole face.

Figs. 21-14 show an alternative form of the invention, only one poletooth being shown with adjacent notches of the coil being-removed. Inthis case the pole is numbered 49.. Its face ad- Fundamentally eachtoothis anvil jacent the gap is shown at 5|, the toe at T and the heel at H.A fragment of the pole ring is shown at 53, with the notches at 55. Thenotches again have sloping bottoms and they are conically shaped so thatthe polar tooth flares away from the inductor in the region of the heelportion H. The tooth flares toward the inductor in the region of the toeportion T (Fig. 14).

Underneaththe toe T, that'oothslopes as shown at 51 forsubstantialparallelism with'the slope of the opposite notch 55.

The pole tooth as shown in Figs. 8-14 is used analogously to the showingin Fig. 1, and an analogous toroidal flux field will be set up having anS-shap'ed mean path through each tooth as shown at S. The varioussections of the pole perpendicular to the S-shape of this field will,after leakage flux between poles is accounted for, have a substantiallyconstant flux density. Enlargement of the face area 5| is arranged inorder tohave a flux density through the face 5| less than the fluxdensities throughout the other sections specified. The enlargement isshown at E.

From the above, it will be clear that broadly the new pole is of anvilshape, the heel of the anvil being associated with the adjacent polering and its toe extending toward the opposite pole ring. The bottom ofthe toe and adjacent flaring notch are essentially parallel. The primaryqualifications for the shape of they anvil are that the toe portionshall be narrower than the heel portion, thereby providing atapering'pole face. The parts of the pole under the toe flare toward thepole'face. The parts under the heel flare away from the pole face towardthe pole ring. The'fianged or overhung edges which lead and trail .inmovement relative to the inductor enlarge the face' area of the polebeyond the area of each other section of the tooth which is normall tothe S-shaped mean flux path through the pole. As a result all of saidother sections carry a constant flux density while the face exclusivelycarries a lower flux density One of the advantages is that a veryefficient flux field is provided, minimizing the magnetizable materialrequired. This is because all sections normal to the S-shaped mean fluxpath carry a constantfiux density after leakage flux has been takeninto'account; except that the flux density through the pole face andacross the flux gap into the inductor is reduced. The reduction in fluxdensity is substantially exclusive to this pole face. The result is thata reduced amount of magnetomotive force is required to force the fieldacross the gap G and the eccentric pull-over force normally associatedwith field members of this type having very small air gaps is reduced.Thus the gap can be held to smaller dimensions without introducingtroubles under slight mechanical eccentricities.

It should be observed that in the form of the invention shown in Figs.1-7, the overhang at is constituted by flat ribs which, as shownjinFigs. 4-7, also flare away from the broader portion of the pole face inthe heel region and flare toward the narrower portion of the face in thetoe region. That is, they have a surface twist. In the form of theinvention shown in Figs. 8-14, the overhang at is not constituted bysuch a particular form of rib but by what in effect amounts to a simpleenlargement starting just under the pole face 5|. 7

The invention is particularly useful in apparatus such as. eddy-currentclutches, brakes, dynaclaimed in the U. S. patent application of RalphL. J aeschke, Serial No. 193,417 for Magnetic Pole, filed November 1,1950.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. For use in a dynamoelectric machine having a rotary inductor and arotary field member composed of an annular field-producing memberpartially surrounded by magnetizable material including notched polerings adjacent to the field member with magnetizable polar teeth of theclaw type extending from the pole rings and interdigitating across thefield member and adjacent to the inductor; a form of said polar teethwherein each comprises a relatively wide heel portion and a relativelynarrow toe portion presenting a pole face adjacent the inductor whichtapers in its direction of extension from its pole ring, the adjacentnotches in its pole ring comprising valleys which are substantiallyconical and increase in size in the direction of the annular fieldmember toeffect a general radial flare of the heel portion away from thepole face in the heel region, the extended portion of the pole beneathits toe portion being tapered down axially but flared radially towardthe narrower pole face, the arrangement being such that cross sectionstaken through the pole substantially normal to the resulting meanS-shaped path of flux passing therethrougli carry a substantiallyconstant flux density, the peripheries of the pole face havingoverhanging narrow edges adapted to enlarge the pole face areasubstantially exclusively at and in the area of the pole face so assubstantially exclusively to reduce the flux density passingtherethrough below that of any of said cross sections.

2. Apparatus made according to claim 1, wherein said overhanging edgesare constituted by rib extension portions.

3. Apparatus made according to claim 2, wherein the lateral faces ofsaid rib portions also flare away from the broader portion of the poleface in the heel region and also flare toward the narrower portion ofthe pole face in the toe region.

MARTIN P. WINTHER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,052,535 Volkers Feb. 11, 19131,502,527 Reichel July 22, 1924 2,470,596 Winther May 17, 1949 FOREIGNPATENTS Number Country Date 235,395 Germany June 9, 1911 OTHERREFERENCES Alternating Current Machinery, Thompson, pages 116-117,published by Spon and Chamberlin, London, 1904.

